Epitaxially Grown Metal-Organic Frameworks: Design, Preparation, and Application as Multi-Component Films in Tandem Catalysis

本项目的目标是利用分子外延技术制备基质支撑的、高度定向的MOFs，并研究这种新型的逐层生长的MOFs在串联催化反应中的应用。这种方法也将带来催化剂不相容性问题的解决方案。此外，使催化剂多相化应大大提高其稳定性，即使在不存在不相容性的情况下。由于MOF具有稳定和结晶的可调结构，我们认为通过仔细的设计在一个单一的MOF中集成多个功能是可行的。在该提案中，为了实现具有高原子和能源效率的可持续有机合成，还强调了使用多功能催化剂开发没有中间分离步骤的一锅级联工艺。我们建议制备一类新的MOFs，为部署两种不同的均相催化剂提供一个令人兴奋的平台，作为下一代选择性和稳定的多相催化剂的构建模块系统.重要的是，这些材料中的催化活性部分可以以位点隔离的方式制备，并且围绕它们的空腔可以在概念上被设计成模拟酶。在该项目中说明了四种不同类型的新型催化剂，包括：i）金属卟啉/salens催化烯烃环氧化，随后捕获CO2以形成环状碳酸酯; ii）金属卟啉催化的C-H胺化，通过原位生成的氮烯，然后利用卡宾等价物进行N-H插入; iii）金属卟啉催化类卡宾插入到S-H键中，然后光诱导所得硫化物的磺基氧化，以及iv）Grubbs第二-从不相容的催化剂（Ir-pincer）生成催化剂，这将导致烷烃复分解。

As exemplified by many catalytic enzyme assemblies in nature, site-isolation is a powerful strategy for performing tandem catalytic reactions to synthesize highly complex molecules.The goals of the project would be to prepare substrate supported, highly oriented MOFs based on the molecular epitaxial approach and then the study of such novel layer-by-layer grown MOFs in tandem catalysis. This approach also would bring a solution to catalysts incompatibility problem. In addition, heterogenizing the catalysts should greatly enhance their stability, even in the absence of an incompatibility. Because MOFs possess tunable structures which are stable and crystalline, we perceived it feasible to integrate multiple functions within one single MOF through a careful design. In this proposal, to achieve sustainable organic synthesis with a high atom and energy efficiency, the development of one-pot cascade processes with no intermediate separation steps using multifunctional catalysts is also highlighted.In this project, we propose to prepare a new class of MOFs providing an exciting platform for deploying two different homogeneous catalysts as building blocks for the next generation of selective and stable heterogeneous catalyst systems. Importantly, the catalytically active moieties in these materials can be made in a site-isolated fashion and the cavities that surround them can be engineered to conceptually to mimic enzymes.Four different classes of novel catalyses are illustrated in the project including: i) metallo- porphyrins/salens catalyzed olefin epoxidation followed by CO2 capture to form cyclic carbonates; ii) metalloporphyrins catalyzed C-H amination via in situ generated nitrenes followed by N-H insertion utilizing carbene equivalents; iii) metalloporphyrins catalyzed insertion of carbenoids into S-H bond followed by photo-induced sulfoxidation of the resulting sulfides and iv) site-isolation of Grubbs second-generation catalysts from the incompatible catalysts (Ir-pincer) which would lead to alkane metathesis.